Method, system, device and medium for evaluating state of lightning arrester based on third harmonic

Abstract

The present application relates to the technical field of power system, and more particularly to a lightning arrester state evaluation method, system, device and medium based on third harmonic, comprising: collecting bus voltage signals of the lightning arrester and leakage currents flowing through the lightning arrester down lead; performing full-cycle Fourier transform on at least two bus voltage signals and Fourier transform on at least two leakage currents to extract grid resistive current third harmonic generated by system voltage third harmonic in the lightning arrester leakage current; excluding the grid resistive current third harmonic interference to obtain the lightning arrester nonlinear third harmonic current amplitude, and evaluating the lightning arrester state according to the lightning arrester nonlinear third harmonic current amplitude obtained twice before and after. The present application extracts and excludes the third harmonic interference caused by system harmonic, thereby accurately reflecting the operation state of the lightning arrester, and has the characteristics of high measurement accuracy, simple operation, strong practicability and stable reliability.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and in particular to a method, system, device and medium for assessing the condition of surge arresters based on third harmonics. Background Technology

[0002] Zinc oxide surge arresters (MOAs) are the main equipment used in power grids to limit overvoltages. The reliable operation of MOAs is crucial to the safe and stable operation of the power grid. As MOAs continue to operate, their performance will decline to some extent.

[0003] Currently, the performance degradation of zinc oxide surge arresters is mainly caused by the aging of the zinc oxide surge arrester resistor elements. The aging of the zinc oxide surge arrester resistor elements will significantly increase the high-order harmonic components (mainly the third harmonic) of the resistive current, that is, the resistive current of the surge arrester contains obvious third harmonics. Once the signs of aging of the surge arrester resistor elements appear, the third harmonic component will increase sharply. Therefore, the third harmonic in the resistive current can very sensitively reflect the characteristics of the surge arrester. Judging the aging of the surge arrester based on the third harmonic is of great significance. However, the actual third harmonic test of the surge arrester is greatly affected by the harmonics of the system power supply. The third harmonic caused by the system harmonic voltage interferes with the test, thereby reducing the sensitivity and greatly reducing the accuracy of the test. Summary of the Invention

[0004] This invention provides a method, system, device, and medium for assessing the condition of surge arresters based on third harmonics. The technical problem it solves is that traditional surge arrester third harmonic testing is greatly affected by system power supply harmonics and cannot eliminate third harmonic interference caused by system harmonics.

[0005] To address the above technical problems, this invention provides a method, system, device, and medium for assessing the condition of surge arresters based on third harmonics.

[0006] In a first aspect, the present invention provides a method for assessing the condition of a surge arrester based on the third harmonic, the method comprising the following steps:

[0007] Collect the bus voltage signal of the surge arrester and the leakage current flowing through the down conductor of the surge arrester;

[0008] Perform a full-cycle Fourier transform on at least two of the bus voltage signals to obtain the system reference voltage fundamental frequency amplitude, system reference voltage fundamental frequency phase, system third harmonic voltage amplitude, and system third harmonic voltage phase;

[0009] Perform Fourier transform on at least two of the leakage currents to obtain the fundamental frequency phase of the total leakage current of the surge arrester and the phase of the third harmonic current of the surge arrester;

[0010] The amplitude of the fundamental resistive current in the leakage current is obtained based on the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester.

[0011] Based on the phase of the third harmonic voltage of the system and the phase of the third harmonic current of the surge arrester, the total amplitude of the third harmonic component of the resistive leakage current in the leakage current is obtained.

[0012] Based on the fundamental resistive current amplitude, the fundamental frequency amplitude of the system reference voltage, and the amplitude of the system third harmonic voltage, the third harmonic of the grid resistive current generated by the third harmonic of the system voltage in the leakage current of the surge arrester is obtained;

[0013] The amplitude of the nonlinear third harmonic current of the surge arrester is obtained based on the total amplitude of the third harmonic component of the resistive current of the power grid and the third harmonic component of the resistive leakage current. The state of the surge arrester is determined based on the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive measurements.

[0014] In a further embodiment, the formula for calculating the third harmonic of the grid resistive current is:

[0015]

[0016] In the formula, This represents the third harmonic of the resistive current in the power grid. Indicates the amplitude of the system's third harmonic voltage; Indicates the fundamental frequency amplitude of the system reference voltage; This indicates the amplitude of the fundamental resistive current.

[0017] In a further embodiment, the formula for calculating the amplitude of the nonlinear third harmonic current of the surge arrester is as follows:

[0018]

[0019] In the formula, This indicates the amplitude of the nonlinear third harmonic current of the surge arrester; This represents the total amplitude of the third harmonic component of the resistive leakage current; This represents the third harmonic of the resistive current in the power grid.

[0020] In a further embodiment, the step of obtaining the amplitude of the fundamental resistive current in the leakage current based on the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester includes:

[0021] Extract the phase components that are the same between the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester to obtain the amplitude of the fundamental resistive current in the leakage current.

[0022] In a further embodiment, the step of obtaining the total amplitude of the resistive leakage current third harmonic component in the leakage current based on the system third harmonic voltage phase and the arrester third harmonic current phase includes:

[0023] Extract the phase components that are the same between the third harmonic voltage phase of the system and the third harmonic current phase of the surge arrester to obtain the total amplitude of the resistive leakage current third harmonic component in the leakage current.

[0024] In a further implementation, the step of determining the state of the surge arrester based on the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive measurements includes:

[0025] The amplitude of the nonlinear third harmonic current of the surge arrester is compared between the two acquisitions to obtain the difference in the nonlinear third harmonic current of the surge arrester.

[0026] The state of the surge arrester is determined based on the difference in the nonlinear third harmonic current of the surge arrester and the preset harmonic current threshold.

[0027] Secondly, the present invention provides a surge arrester condition assessment system based on third harmonics, the system comprising:

[0028] The data acquisition module is used to acquire the bus voltage signal of the surge arrester and the leakage current flowing through the surge arrester's down conductor;

[0029] The signal processing module is used to perform full-cycle Fourier transform on at least two of the bus voltage signals to obtain the system reference voltage fundamental frequency amplitude, system reference voltage fundamental frequency phase, system third harmonic voltage amplitude, and system third harmonic voltage phase; it is also used to perform Fourier transform on at least two of the leakage currents to obtain the arrester total leakage current fundamental frequency phase and arrester third harmonic current phase.

[0030] The first acquisition module is used to acquire the amplitude of the fundamental resistive current in the leakage current based on the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester; acquire the total amplitude of the third harmonic component of the resistive leakage current in the leakage current based on the phase of the third harmonic voltage of the system and the phase of the third harmonic current of the surge arrester; and obtain the third harmonic of the grid resistive current generated by the third harmonic of the system voltage in the leakage current of the surge arrester based on the amplitude of the fundamental resistive current, the fundamental frequency amplitude of the system reference voltage, and the amplitude of the third harmonic voltage of the system.

[0031] The second acquisition module is used to obtain the amplitude of the nonlinear third harmonic current of the surge arrester based on the total amplitude of the third harmonic component of the resistive current of the power grid and the third harmonic component of the resistive leakage current.

[0032] The status assessment module is used to determine the status of the surge arrester based on the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive measurements.

[0033] In a further embodiment, the formula for calculating the third harmonic of the grid resistive current is:

[0034]

[0035] In the formula, This represents the third harmonic of the resistive current in the power grid. Indicates the amplitude of the system's third harmonic voltage; Indicates the fundamental frequency amplitude of the system reference voltage; This indicates the amplitude of the fundamental resistive current.

[0036] Thirdly, the present invention also provides a computer device, including a processor and a memory, the processor being connected to the memory, the memory being used to store a computer program, and the processor being used to execute the computer program stored in the memory, so that the computer device performs the steps of implementing the above-described method.

[0037] Fourthly, the present invention also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method.

[0038] This invention provides a method, system, device, and medium for surge arrester condition assessment based on the third harmonic. The method extracts the third harmonic of the grid resistive current generated by the third harmonic of the system voltage in the surge arrester's leakage current by performing full-cycle Fourier transforms on at least two bus voltage signals and Fourier transforms on at least two leakage currents. This allows for the acquisition of the amplitude of the surge arrester's nonlinear third harmonic current, achieving accurate assessment of the surge arrester's condition. Compared to existing technologies, this method reliably inverts the amplitude of the surge arrester's nonlinear third harmonic current based on the higher harmonics of the leakage current, sets a threshold, and diagnoses the surge arrester's operating status, ensuring the safe operation of the surge arrester. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the surge arrester condition assessment method based on the third harmonic provided in an embodiment of the present invention;

[0040] Figure 2 This is an equivalent diagram of a zinc oxide surge arrester provided in an embodiment of the present invention;

[0041] Figure 3 This is a block diagram of a surge arrester condition assessment system based on third harmonics provided in an embodiment of the present invention;

[0042] Figure 4This is a schematic diagram of the structure of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0043] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0044] refer to Figure 1 This invention provides a method for assessing the condition of surge arresters based on third harmonics, such as... Figure 1 As shown, the method includes the following steps:

[0045] S1. Collect the bus voltage signal of the surge arrester and the leakage current flowing through the surge arrester's down conductor.

[0046] S2. Perform a full-cycle Fourier transform on at least two of the bus voltage signals to obtain the system reference voltage fundamental frequency amplitude, system reference voltage fundamental frequency phase, system third harmonic voltage amplitude, and system third harmonic voltage phase.

[0047] This embodiment acquires the bus voltage signal of the surge arrester by means of voltage sensors (such as current transformers, capacitive voltage dividers, etc.), and performs a full-cycle Fourier operation on the acquired signal of at least two cycles every N sampling points to obtain the fundamental frequency amplitude of the system reference voltage. System reference voltage fundamental frequency phase The amplitude of the third harmonic voltage of the system Phase of the system's third harmonic voltage .

[0048] S3. Perform Fourier transform on at least two of the leakage currents to obtain the fundamental frequency phase of the total leakage current of the surge arrester and the phase of the third harmonic current of the surge arrester.

[0049] In this embodiment, the leakage current flowing through the arrester's down conductor is measured simultaneously. Fourier transforms are performed on the acquired signals of at least two cycles every N sampling points to obtain the fundamental frequency amplitude of the arrester's total leakage current. Total leakage current of surge arrester, fundamental frequency phase The amplitude of the third harmonic current of the surge arrester Phase of the third harmonic current of the surge arrester .

[0050] Figure 2 The diagram shows the equivalent value of a zinc oxide surge arrester, where R is a nonlinear element of the zinc oxide surge arrester. The volt-ampere characteristic of this nonlinear element can be expressed by the following polynomial:

[0051]

[0052] The fundamental frequency component of the applied voltage is represented as a sinusoidal voltage. Furthermore, considering that lower-order harmonics have a greater impact on the arrester's state than higher-order harmonics, the expression for the arrester's nonlinear element is simplified as follows:

[0053]

[0054] The leakage current generated on the surge arrester by the system fundamental voltage is:

[0055]

[0056] If the applied voltage contains the third harmonic voltage, it can be represented as: The expression for the nonlinear element of the surge arrester is still simplified as follows:

[0057]

[0058] but It can be written as:

[0059]

[0060] It is evident that the third harmonic of the system generates third and ninth harmonics or higher in the resistive component of the surge arrester leakage current. Ignoring the ninth and higher harmonics in the above formula (because these components have very small amplitudes), and retaining only the third and lower harmonics, the surge arrester resistive current considering the grid fundamental frequency and the third harmonic is calculated. It can be represented as:

[0061]

[0062] in,

[0063]

[0064]

[0065] In the formula, This embodiment represents the fundamental resistive component of the leakage current (which can be obtained through testing). Amplitude is expressed as ; This represents the total third harmonic component of the system and the third harmonic component of the surge arrester leakage current caused by the surge arrester's nonlinearity, where... This embodiment will Amplitude is expressed as ; This represents the total amplitude of the third harmonic component of the resistive leakage current; This embodiment represents the third harmonic of the surge arrester leakage current caused by the nonlinearity of the surge arrester. Amplitude is expressed as ; This indicates the amplitude of the nonlinear third harmonic current of the surge arrester; This embodiment represents the third harmonic of the surge arrester leakage current caused by the third harmonic of the system. Amplitude is expressed as ; The value represents the third harmonic of the resistive current in the power grid; w represents the angular frequency; and t represents time.

[0066] Therefore, it can be seen that due to interference from system power supply harmonics, the third harmonic component of the resistive leakage current... This mainly includes the third harmonic of the resistive current generated by the nonlinearity of the surge arrester when the fundamental wave of the power grid passes through it. And the resistive current third harmonic generated when the system voltage third harmonic passes through the surge arrester. If it can be deducted from the third harmonic of the total resistive leakage current The remaining portion is the third harmonic current caused by the nonlinearity of the surge arrester itself. The level of this third harmonic current reflects the nonlinearity of the surge arrester itself, and it increases rapidly when the surge arrester is defective. Therefore, if the third harmonic current generated by the third harmonic voltage of the power grid on the surge arrester is extracted, the power grid interference can be eliminated.

[0067] S4. Based on the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester, obtain the amplitude of the fundamental resistive current in the leakage current.

[0068] This embodiment uses wireless communication methods (such as Bluetooth, Wi-Fi, etc.) to realize data transmission between the voltage monitoring device and the current sensor, by using the system reference voltage base frequency phase. and the fundamental frequency phase of the total leakage current of the surge arrester By comparison, the fundamental frequency phase of the system reference voltage is extracted. and the fundamental frequency phase of the total leakage current of the surge arrester The amplitude of the fundamental resistive current in the leakage current is obtained by using the same phase components between them. .

[0069] S5. Based on the phase of the third harmonic voltage of the system and the phase of the third harmonic current of the surge arrester, obtain the total amplitude of the third harmonic component of the resistive leakage current in the leakage current.

[0070] This embodiment will specify the phase of the system's third harmonic voltage. Phase of the third harmonic current of the surge arrester By comparison, the phase of the third harmonic voltage of the system is extracted. and the phase of the third harmonic current of the surge arrester The same phase components between them yield the total amplitude of the third harmonic component of the resistive leakage current in the leakage current. .

[0071] S6. Based on the fundamental resistive current amplitude, the fundamental frequency amplitude of the system reference voltage, and the amplitude of the system third harmonic voltage, the third harmonic of the system voltage is obtained as the third harmonic of the grid resistive current generated in the leakage current of the surge arrester.

[0072] In this embodiment, to calculate the amplitude of the third harmonic of the system voltage generated as the third harmonic of the grid resistive current in the surge arrester leakage current, it is necessary to calculate its amplitude. However, the expression for the third harmonic component of the grid resistive current contains... , , Since the unknown quantity cannot be directly solved, but considering:

[0073]

[0074] That is, there is a proportional relationship between the amplitudes of the two, which can be realized by the following formula: the third harmonic of the system voltage generates the third harmonic of the resistive current when it passes through the surge arrester. Calculation:

[0075]

[0076] In the formula, This represents the third harmonic of the resistive current in the power grid. Indicates the amplitude of the system's third harmonic voltage; Indicates the fundamental frequency amplitude of the system reference voltage; This indicates the amplitude of the fundamental resistive current.

[0077] S7. Based on the total amplitude of the third harmonic component of the resistive current of the power grid and the third harmonic component of the resistive leakage current, the amplitude of the nonlinear third harmonic current of the surge arrester is obtained, and the state of the surge arrester is determined based on the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive tests.

[0078] In one embodiment, the formula for calculating the amplitude of the nonlinear third harmonic current of the surge arrester is as follows:

[0079]

[0080] In the formula, This indicates the amplitude of the nonlinear third harmonic current of the surge arrester; This represents the total amplitude of the third harmonic component of the resistive leakage current; This represents the third harmonic of the resistive current in the power grid.

[0081] This embodiment compares the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive measurements to obtain the difference in the nonlinear third harmonic current of the surge arrester. Based on the difference in the nonlinear third harmonic current of the surge arrester and the preset harmonic current threshold, the state of the surge arrester is determined. For example, if the difference in the nonlinear third harmonic current of the surge arrester exceeds the preset harmonic current threshold (e.g., 50%), monitoring should be strengthened. When it increases significantly (e.g., exceeding the previous value by 100%), the power should be cut off and maintenance should be carried out immediately.

[0082] This embodiment provides a surge arrester condition assessment method based on the third harmonic. The method fully utilizes the proportional relationship between the fundamental component of the surge arrester's resistive current and the third harmonic current caused by the third harmonic of the system voltage to obtain the third harmonic value caused by the system, thereby eliminating third harmonic interference caused by the system and accurately solving for the third harmonic current caused by the surge arrester's nonlinearity, achieving an accurate assessment of the surge arrester's condition. Compared with existing technologies, this application achieves simultaneous comparison of multiple key parameters of the surge arrester based on synchronous time synchronization and wireless communication, enabling comprehensive analysis of the relationship between harmonics and the fundamental frequency component, and more accurately calculating the nonlinear characteristics of the surge arrester. This provides a precise and reliable assessment of the surge arrester's condition, offering the clearest and most accurate data for judgment in surge arrester condition-based maintenance.

[0083] It should be noted that the sequence number of each process does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0084] In one embodiment, such as Figure 3 As shown, this embodiment provides a surge arrester condition assessment system based on the third harmonic, the system comprising:

[0085] Data acquisition module 101 is used to acquire the bus voltage signal of the surge arrester and the leakage current flowing through the surge arrester's down conductor;

[0086] The signal processing module 102 is used to perform full-cycle Fourier transform on at least two of the bus voltage signals to obtain the system reference voltage fundamental frequency amplitude, system reference voltage fundamental frequency phase, system third harmonic voltage amplitude, and system third harmonic voltage phase; it is also used to perform Fourier transform on at least two of the leakage currents to obtain the arrester total leakage current fundamental frequency phase and arrester third harmonic current phase.

[0087] The first acquisition module 103 is used to acquire the amplitude of the fundamental resistive current in the leakage current based on the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester; acquire the amplitude of the resistive third harmonic current in the leakage current based on the phase of the third harmonic voltage of the system and the phase of the third harmonic current of the surge arrester; and obtain the third harmonic of the grid resistive current generated by the third harmonic of the system voltage in the leakage current of the surge arrester based on the amplitude of the fundamental resistive current, the fundamental frequency amplitude of the system reference voltage, and the amplitude of the third harmonic voltage of the system.

[0088] The second acquisition module 104 is used to obtain the amplitude of the nonlinear third harmonic current of the surge arrester based on the third harmonic of the resistive current of the power grid and the amplitude of the resistive third harmonic current.

[0089] The status assessment module 105 is used to determine the status of the surge arrester based on the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive measurements.

[0090] In one embodiment, the formula for calculating the third harmonic of the grid resistive current is:

[0091]

[0092] In the formula, This represents the third harmonic of the resistive current in the power grid. Indicates the amplitude of the system's third harmonic voltage; Indicates the fundamental frequency amplitude of the system reference voltage; This indicates the amplitude of the fundamental resistive current.

[0093] For specific limitations regarding a surge arrester condition assessment system based on third harmonics, please refer to the above-described limitations regarding a surge arrester condition assessment method based on third harmonics, which will not be repeated here. Those skilled in the art will recognize that the various modules and steps described in conjunction with the embodiments disclosed in this application can be implemented in hardware, software, or a combination of both. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0094] This invention provides a surge arrester condition assessment system based on third harmonics. The system acquires the bus voltage signal and leakage current flowing through the arrester's down conductor via a data acquisition module. A signal processing module performs full-cycle Fourier transform and Fourier transform on the bus voltage signal and leakage current, respectively. A first acquisition module and a second acquisition module extract the third harmonic interference caused by the system, thereby accurately calculating the third harmonic current caused by the arrester's nonlinearity. Compared with existing technologies, this application calculates the system-induced third harmonic resistive current based on the proportional relationship between the fundamental component of the arrester's resistive current and the third harmonic current caused by the system voltage's third harmonic, thereby eliminating the system-induced third harmonic resistive current and obtaining the third harmonic current caused by the arrester's nonlinearity. It is simple to operate, safe and reliable, and can accurately measure the third harmonic current caused by the arrester's nonlinearity, accurately judge the arrester's condition, and provide a reliable basis for formulating arrester maintenance plans.

[0095] Figure 4 This invention provides a computer device including a memory, a processor, and a transceiver, which are connected to each other via a bus. The memory is used to store a set of computer program instructions and data, and can transmit the stored data to the processor. The processor can execute the program instructions stored in the memory to perform the steps of the above method.

[0096] The memory may include volatile memory or non-volatile memory, or both; the processor may be a central processing unit, a microprocessor, an application-specific integrated circuit, a programmable logic device, or a combination thereof. By way of example, but not limitation, the programmable logic device described above may be a complex programmable logic device, a field-programmable gate array, a general-purpose array logic, or any combination thereof.

[0097] In addition, memory can be a physically independent unit or integrated with the processor.

[0098] Those skilled in the art will understand that Figure 4 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have the same component arrangement.

[0099] In one embodiment, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the above-described method.

[0100] The present invention provides a surge arrester condition assessment method, system, device and medium based on third harmonics. The surge arrester condition assessment method based on third harmonics is based on the inversion of higher harmonics of leakage current to obtain the third harmonic current caused by the nonlinearity of the surge arrester, which is of great significance for ensuring the safe operation of power equipment.

[0101] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present invention are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., SSD), etc.

[0102] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when the computer program is executed, it can include the processes of the embodiments of the above methods.

[0103] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various improvements and substitutions without departing from the technical principles of this invention, and these improvements and substitutions should also be considered within the scope of protection of this application. Therefore, the scope of protection of this patent application should be determined by the scope of the claims.

Claims

1. A method for assessing the condition of a surge arrester based on third harmonics, characterized in that, Includes the following steps: Collect the bus voltage signal of the surge arrester and the leakage current flowing through the down conductor of the surge arrester; Perform a full-cycle Fourier transform on at least two of the bus voltage signals to obtain the system reference voltage fundamental frequency amplitude, system reference voltage fundamental frequency phase, system third harmonic voltage amplitude, and system third harmonic voltage phase; Perform Fourier transform on at least two of the leakage currents to obtain the fundamental frequency phase of the total leakage current of the surge arrester and the phase of the third harmonic current of the surge arrester; The amplitude of the fundamental resistive current in the leakage current is obtained based on the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester. Based on the phase of the third harmonic voltage of the system and the phase of the third harmonic current of the surge arrester, the total amplitude of the third harmonic component of the resistive leakage current in the leakage current is obtained. Based on the fundamental resistive current amplitude, the fundamental frequency amplitude of the system reference voltage, and the amplitude of the system third harmonic voltage, the third harmonic of the grid resistive current generated by the third harmonic of the system voltage in the surge arrester leakage current is obtained; the calculation formula for the third harmonic of the grid resistive current is: In the formula, This represents the third harmonic of the resistive current in the power grid. Indicates the amplitude of the system's third harmonic voltage; Indicates the fundamental frequency amplitude of the system reference voltage; Indicates the amplitude of the fundamental resistive current; The amplitude of the nonlinear third harmonic current of the surge arrester is obtained based on the total amplitude of the third harmonic component of the resistive current of the power grid and the third harmonic component of the resistive leakage current. The state of the surge arrester is determined based on the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive measurements.

2. The surge arrester condition assessment method based on third harmonic as described in claim 1, characterized in that, The formula for calculating the amplitude of the nonlinear third harmonic current of the surge arrester is as follows: In the formula, This indicates the amplitude of the nonlinear third harmonic current of the surge arrester; This represents the total amplitude of the third harmonic component of the resistive leakage current; This represents the third harmonic of the resistive current in the power grid.

3. The surge arrester condition assessment method based on third harmonic as described in claim 1, characterized in that, The step of obtaining the amplitude of the fundamental resistive current in the leakage current based on the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester includes: Extract the phase components that are the same between the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester to obtain the amplitude of the fundamental resistive current in the leakage current.

4. The surge arrester condition assessment method based on third harmonic as described in claim 1, characterized in that, The step of obtaining the total amplitude of the resistive leakage current third harmonic component in the leakage current based on the phase of the third harmonic voltage of the system and the phase of the third harmonic current of the surge arrester includes: Extract the phase components that are the same between the third harmonic voltage phase of the system and the third harmonic current phase of the surge arrester to obtain the total amplitude of the resistive leakage current third harmonic component in the leakage current.

5. The surge arrester condition assessment method based on third harmonic as described in claim 1, characterized in that, The step of determining the state of the surge arrester based on the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive measurements includes: The amplitude of the nonlinear third harmonic current of the surge arrester is compared between the two acquisitions to obtain the difference in the nonlinear third harmonic current of the surge arrester. The state of the surge arrester is determined based on the difference in the nonlinear third harmonic current of the surge arrester and the preset harmonic current threshold.

6. A surge arrester condition assessment system based on third harmonics, characterized in that, The system includes: The data acquisition module is used to acquire the bus voltage signal of the surge arrester and the leakage current flowing through the surge arrester's down conductor; The signal processing module is used to perform full-cycle Fourier transform on at least two of the bus voltage signals to obtain the system reference voltage fundamental frequency amplitude, system reference voltage fundamental frequency phase, system third harmonic voltage amplitude, and system third harmonic voltage phase; it is also used to perform Fourier transform on at least two of the leakage currents to obtain the arrester total leakage current fundamental frequency phase and arrester third harmonic current phase. The first acquisition module is used to acquire the amplitude of the fundamental resistive current in the leakage current based on the fundamental frequency phase of the system reference voltage and the fundamental frequency phase of the total leakage current of the surge arrester; to acquire the total amplitude of the third harmonic component of the resistive leakage current in the leakage current based on the phase of the third harmonic voltage of the system and the phase of the third harmonic current of the surge arrester; and to obtain the third harmonic of the grid resistive current generated by the third harmonic of the system voltage in the leakage current of the surge arrester based on the amplitude of the fundamental resistive current, the fundamental frequency amplitude of the system reference voltage, and the amplitude of the third harmonic voltage of the system; the calculation formula for the third harmonic of the grid resistive current is: In the formula, This represents the third harmonic of the resistive current in the power grid. Indicates the amplitude of the system's third harmonic voltage; Indicates the fundamental frequency amplitude of the system reference voltage; Indicates the amplitude of the fundamental resistive current; The second acquisition module is used to obtain the amplitude of the nonlinear third harmonic current of the surge arrester based on the total amplitude of the third harmonic component of the resistive current of the power grid and the third harmonic component of the resistive leakage current. The status assessment module is used to determine the status of the surge arrester based on the amplitude of the nonlinear third harmonic current of the surge arrester obtained in two consecutive measurements.

7. A computer device, characterized in that: The device includes a processor and a memory, the processor being connected to the memory for storing computer programs, and the processor for executing the computer programs stored in the memory to cause the computer device to perform the method as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program that, when executed, implements the method as described in any one of claims 1 to 5.

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